U.S. patent application number 12/464807 was filed with the patent office on 2010-11-18 for systems and methods for using secondary fuels.
Invention is credited to Chris M. Cologna.
Application Number | 20100292911 12/464807 |
Document ID | / |
Family ID | 43069208 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100292911 |
Kind Code |
A1 |
Cologna; Chris M. |
November 18, 2010 |
SYSTEMS AND METHODS FOR USING SECONDARY FUELS
Abstract
The present application provides a system and method for
determining a secondary fuel amount for an engine. The method
comprises measuring an injector signal from an engine's Engine
Control Unit (ECU) for a primary injector. A delay time of the
primary injector can be determined using a lookup table. An open
time can be calculated based on the delay time and the primary
timing value. An amount of fuel to be injected into the engine can
be calculated based on the primary injector open time. An amount of
secondary fuel equivalent to the amount of primary fuel can be
determined. A timing value for a secondary injector signal for the
secondary injector can be calculated to deliver the amount of
secondary fuel to the engine.
Inventors: |
Cologna; Chris M.;
(Bountiful, UT) |
Correspondence
Address: |
THORPE NORTH & WESTERN, LLP.
P.O. Box 1219
SANDY
UT
84091-1219
US
|
Family ID: |
43069208 |
Appl. No.: |
12/464807 |
Filed: |
May 12, 2009 |
Current U.S.
Class: |
701/104 ;
123/299; 123/304 |
Current CPC
Class: |
F02D 41/20 20130101;
Y02T 10/44 20130101; F02D 2041/2051 20130101; Y02T 10/40 20130101;
F02D 41/3094 20130101; F02D 2200/0602 20130101; F02D 2400/11
20130101; F02D 41/401 20130101; F02D 41/0025 20130101 |
Class at
Publication: |
701/104 ;
123/304; 123/299 |
International
Class: |
F02D 41/30 20060101
F02D041/30; F02M 43/00 20060101 F02M043/00; F02B 3/00 20060101
F02B003/00 |
Claims
1. A method of determining a secondary fuel amount for an engine,
comprising: measuring an injector signal from an engine's Engine
Control Unit (ECU) for a primary injector for a primary fuel to
determine a primary timing value for the primary injector;
determining a delay time of the primary injector using a lookup
table configured to provide the delay time of the primary injector
to determine an open time of the primary injector based on a
difference between the primary timing value and the delay time, the
open time being used to calculate an amount of the primary fuel to
be injected into the engine during the primary injector's open
time, based on the injector signal; determining an amount of
secondary fuel equivalent to the amount of primary fuel; and
calculating a secondary timing value for a secondary injector
signal for a secondary injector to deliver the amount of secondary
fuel to the engine in place of the primary fuel.
2. The method of claim 1, wherein determining an open time further
comprises measuring a pressure differential of the primary fuel and
a voltage of the primary injector.
3. The method of claim 2, further comprising determining a delay
time associated with the primary injector from the pressure
differential and the voltage using a lookup table.
4. The method of claim 3, further comprising calculating an open
time of the primary injector by subtracting the delay time from the
primary timing value of the primary injector.
5. The method of claim 4, further comprising determining the amount
of primary fuel to be delivered to the engine based on the injector
signal by multiplying a flow rate of the primary fuel times the
open time of the primary injector.
6. The method of claim 1, further comprising measuring a pressure
differential of the secondary fuel.
7. The method of claim 1, further comprising measuring a voltage of
the secondary injector used to inject the secondary fuel.
8. The method of claim 7, further comprising calculating a delay
time associated with the secondary injector from the secondary fuel
pressure and the secondary injector voltage using a lookup
table.
9. The method of claim 8, wherein calculating the secondary timing
value for the secondary injector further comprises adding the delay
time of the secondary injector with an open time of the secondary
injector sufficient to deliver the amount of secondary fuel to the
engine.
10. The method of claim 1, wherein determining the amount of
secondary fuel further comprises calculating an energy value
associated with the amount of primary fuel and calculating the
amount of secondary fuel needed to provide the energy value.
11. A secondary fuel control system for an engine, comprising: a
detector configured to detect a timing value from an Engine Control
Unit (ECU) injection signal for a primary injector; a lookup table
coupled to the detector and configured to provide a delay time of
the primary injector to determine an open time of the primary
injector based on a difference between the timing value and the
delay value, the open time being used to calculate a predetermined
amount of the primary fuel to be injected into the engine during
the primary injector's open time based on the ECU injection signal;
and a secondary fuel equivalent module coupled to the lookup table
and configured to calculate an amount of a secondary fuel having an
energy equivalent to the predetermined amount of primary fuel by
calculating an energy value of the predetermined amount of primary
fuel, calculating the amount of the secondary fuel needed to
provide the energy equivalent, and calculating a secondary timing
value for a secondary injector to inject the energy equivalent of
the secondary fuel into the engine in place of the primary
fuel.
12. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module is further configured to receive
at least one signal containing information of a fuel pressure for
the primary fuel and a voltage at the primary injector to calculate
the delay time of the primary injector.
13. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module is further configured to receive a
signal containing information of a low side fuel pressure for the
secondary fuel and a high side pressure of the secondary fuel to
calculate a flow rate of the secondary fuel.
14. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module is further configured to receive a
signal containing information of a tank pressure for the secondary
fuel to calculate a fuel level signal for the secondary fuel.
15. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module is further configured to receive a
signal containing information of a temperature for the secondary
fuel to calculate a density of the secondary fuel.
16. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module is further configured to send a
signal containing information of a fuel pressure for the primary
fuel for use by the ECU.
17. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module is further configured to send a
signal containing information of a fuel level for the secondary
fuel for use by a fuel level indicator.
18. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module is further configured to send a
signal containing information of an injector pulse for the
secondary injector for the secondary fuel corresponding to the
secondary timing value.
19. The secondary fuel control system of claim 11, wherein the
secondary fuel equivalent module further comprises a communication
port for programming and diagnostic testing.
20. The secondary fuel control system of claim 11, wherein the
amount of secondary fuel calculated from the energy value of the
primary fuel accounts for the delay times of the primary injector
and the secondary injector.
21. A secondary fuel control system for an engine, comprising: a
detector configured to detect a timing value from an Engine Control
Unit (ECU) injection signal for a primary injector; a first lookup
table coupled to the detector and configured to provide a delay
time of the primary injector for injecting a predetermined amount
of a primary fuel into the engine; a second lookup table coupled to
a secondary fuel equivalent module and configured to provide a
ratio of secondary fuel to primary fuel for the engine; a secondary
fuel equivalent module coupled to the first lookup table and the
second lookup table; the secondary fuel equivalent module
configured to calculate an amount of a secondary fuel having an
energy equivalent based on the ratio of secondary fuel to primary
fuel by calculating an energy value of the predetermined amount of
primary fuel, calculating an amount of the secondary fuel needed to
supplement the primary fuel to provide the ratio, and calculating a
secondary timing value for a second injector to inject the energy
equivalent of the secondary fuel into the engine.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to mechanical
systems and methods. More particularly, the present invention
relates to using secondary fuels in engines.
BACKGROUND
[0002] Engines and mechanical devices have long been dependent upon
fossil fuels. Petroleum products have provided 96 percent of
America's transportation energy needs. However, such usage has had
environmental impacts. Specifically, using petroleum products in
engines is known to cause pollution and increase greenhouse gasses.
In addition to carbon dioxide, combustion of fossil fuels is known
to create noxious byproducts (NO.sub.x, CO.sub.x, etc.).
Additionally, the rising costs of petroleum products can cause
significant economic impact. As such, research and development into
alternate fuels is continually sought. Such fuels include
electricity, hydrogen, natural gas, etc.
SUMMARY OF THE INVENTION
[0003] In light of the foregoing, the Applicants have recognized a
need to develop systems and methods that can determine and/or
deliver a secondary fuel to replace or supplement a primary fuel in
an engine. Accordingly, the present application provides for a
method of supplying a secondary fuel to an engine. The method
comprises measuring an injector signal from the engine's engine
control unit (ECU) for a primary injector for a primary fuel to
determine a timing value for the primary injector. Additionally,
the method can include determining a delay time of the primary
injector using a lookup table configured to provide the delay time
of the primary injector. The delay time can be used to determine an
open time of the primary injector based on a difference between the
primary timing value and the delay time. The open time can be used
to calculate a predetermined amount of the primary fuel to be
injected into the engine during the primary injector's open time
according to the injector signal. Further the method can include
determining an amount of secondary fuel equivalent to the primary
fuel. Such a method can also include calculating a secondary timing
value for a secondary injector signal for the secondary injector to
deliver the amount of secondary fuel to the engine.
[0004] In another embodiment, a secondary fuel control system for
an engine can comprise a detector configured to detect a timing
value from an ECU injection signal for a primary injector. The
secondary fuel control system can include a lookup table coupled to
the detector and configured to provide a delay time of the primary
injector for injecting a predetermined amount of the primary fuel
into the engine. Additionally, the secondary fuel control system
can include a secondary fuel equivalent module coupled to the
lookup table and configured to calculate an amount of a secondary
fuel having an energy equivalent to the predetermined amount of
primary fuel by calculating an energy value of the predetermined
amount of primary fuel, calculating the amount of the secondary
fuel needed to provide the energy equivalent, and calculating a
secondary timing value for a second injector to inject the energy
equivalent of the secondary fuel into the engine in place of the
primary fuel.
[0005] In still another embodiment, a secondary fuel control system
for an engine can comprise a detector configured to detect a timing
value from an ECU injection signal for a primary injector. The
secondary fuel control system can include a first lookup table
coupled to the detector and configured to provide a delay time of
the primary injector for injecting a predetermined amount of the
primary fuel into the engine and a second lookup table coupled to a
secondary fuel equivalent module and configured to provide a ratio
of secondary fuel to primary fuel for the engine. The secondary
fuel control system can include a secondary fuel equivalent module
coupled to the first lookup table and the second lookup table such
that the secondary fuel equivalent module is configured to
calculate an amount of a secondary fuel having an energy equivalent
based on the ratio of secondary fuel to primary fuel by calculating
an energy value of the predetermined amount of primary fuel,
calculating the amount of the secondary fuel needed to supplement
the primary fuel to provide the ratio, and calculating a secondary
timing value for a second injector to inject the energy equivalent
of the secondary fuel into the engine.
[0006] Additional features and advantages of the invention will be
apparent from the following detailed description, which
illustrates, by way of example, features of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Additional features and advantages of the invention will be
apparent from the detailed description which follows, taken in
conjunction with the accompanying drawings, which together
illustrate, by way of example, features of the invention.
[0008] FIG. 1 is a table showing injector delay times based on
injector voltage and fuel pressure in accordance with an embodiment
of the present invention.
[0009] FIG. 2 is a schematic flow diagram illustrating one
embodiment of a method for supplying a secondary fuel to an engine
in accordance with the present application;
[0010] FIG. 3 is a schematic diagram of one embodiment of the
system of the present invention; and
[0011] FIG. 4 is an enlarged view of the secondary fuel control
system in accordance with an embodiment of the present
invention.
[0012] Reference will now be made to the exemplary embodiments
illustrated, and specific language will be used herein to describe
the same. It will nevertheless be understood that no limitation of
the scope of the invention is thereby intended.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0013] Before particular embodiments of the present invention are
disclosed and described, it is to be understood that this invention
is not limited to the particular process and materials disclosed
herein as such may vary to some degree. It is also to be understood
that the terminology used herein is used for the purpose of
describing particular embodiments only and is not intended to be
limiting. The scope of the present invention will be defined only
by the appended claims and equivalents thereof.
[0014] In describing and claiming the present invention, the
following terminology will be used.
[0015] The singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise. Thus, for
example, reference to "an injector" includes reference to one or
more of such injectors.
[0016] As used herein, the term "about" is used to provide
flexibility to a numerical range endpoint by providing that a given
value may be "a little above" or "a little below" the endpoint. The
degree of flexibility of this term can be dictated by the
particular variable and would be within the knowledge of those
skilled in the art to determine based on experience and the
associated description herein.
[0017] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the
contrary.
[0018] Concentrations, amounts, and other numerical data may be
expressed or presented herein in a range format. It is to be
understood that such a range format is used merely for convenience
and brevity and thus should be interpreted flexibly to include not
only the numerical values explicitly recited as the limits of the
range, but also to include all the individual numerical values or
sub-ranges encompassed within that range as if each numerical value
and sub-range is explicitly recited. As an illustration, a
numerical range of "about 0.01 to 2.0 mm" should be interpreted to
include not only the explicitly recited values of about 0.01 mm to
about 2.0 mm, but also include individual values and sub-ranges
within the indicated range. Thus, included in this numerical range
are individual values such as 0.5, 0.7, and 1.5, and sub-ranges
such as from 0.5 to 1.7, 0.7 to 1.5, and from 1.0 to 1.5, etc.
Furthermore, such an interpretation should apply regardless of the
breadth of the range or the characteristics being described.
[0019] It should be understood that many of the functional units
described in this specification have been labeled as modules, in
order to more particularly emphasize their implementation
independence. For example, a module may be implemented as a
hardware circuit comprising custom VLSI circuits or gate arrays,
off-the-shelf semiconductors such as logic chips, transistors, or
other discrete components. A module may also be implemented in
programmable hardware devices such as field programmable gate
arrays, programmable array logic, programmable logic devices or the
like.
[0020] Modules may also be implemented in software for execution by
various types of processors. An identified module of executable
code may, for instance, comprise one or more physical or logical
blocks of computer instructions, which may, for instance, be
organized as an object, procedure, or function. Nevertheless, the
executables of an identified module need not be physically located
together, but may comprise disparate instructions stored in
different locations which, when joined logically together, comprise
the module and achieve the stated purpose for the module.
[0021] Indeed, a module of executable code may be a single
instruction, or many instructions, and may even be distributed over
several different code segments, among different programs, and
across several memory devices. Similarly, operational data may be
identified and illustrated herein within modules, and may be
embodied in any suitable form and organized within any suitable
type of data structure. The operational data may be collected as a
single data set, or may be distributed over different locations
including over different storage devices, and may exist, at least
partially, merely as electronic signals on a system or network. The
modules may be passive or active, including agents operable to
perform desired functions.
[0022] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the present invention. Thus,
appearances of the phrases "in one embodiment" or "in an
embodiment" in various places throughout this specification are not
necessarily all referring to the same embodiment.
[0023] The described features, structures or characteristics
described herein may be combined in any suitable manner in one or
more embodiments. Furthermore, one skilled in the relevant art will
recognize that the invention can be practiced without one or more
of the specific details, methods, components, materials, etc. In
other instances, well-known components, methods, structures, and
materials may not be shown or described in detail to avoid
obscuring aspects of the invention.
[0024] It has been recognized that it would be advantageous to
develop a secondary fuel control system for determining and/or
delivering a secondary fuel to replace or supplement a primary fuel
in an engine. For example, the secondary fuel control system can be
used to deliver a secondary fuel such as compressed natural gas to
replace gasoline used in an engine designed to operate with
gasoline fuel. Alternatively, the secondary fuel control system can
be used to supplement diesel fuel used in a diesel engine designed
to operate with diesel fuel. Other types of secondary fuels that
can be used as a replacement or supplement include propane,
hydrogen, biodiesel, bioalcohol (methanol, ethanol, butanol),
non-fossil methane, non-fossil natural gas, vegetable oil, and
other biomass sources. A secondary fuel, as used herein, is
considered to be any type of chemical fuel for which the engine was
not specifically designed that contains sufficient energy to enable
the engine to operate within the engine's design parameters. Thus,
the secondary fuel control system may be used to convert an engine
to operate on or be supplemented with a secondary fuel such as
gasoline or diesel fuel when the engine is specifically designed to
operate using hydrogen as a primary fuel.
[0025] The secondary fuel control system enables an engine to use
these secondary fuels in a manner that will enable the engine to
operate in accordance with its design parameters. By operating the
engine within its design parameters, engine emissions can be
minimized, thereby enabling the secondary fuel to be used in an
efficient manner while diminishing the environmental effects of
using the secondary fuel.
[0026] In accordance with this, the present invention is drawn to
systems and methods having a detector, a look-up table, and a
secondary fuel equivalent module. It is noted that when discussing
a secondary fuel control system or a method of supplying a
secondary fuel to an engine, each of these discussions can be
considered applicable to each of these embodiments, whether or not
they are explicitly discussed in the context of that embodiment.
Thus, for example, in discussing a primary injector for a secondary
fuel control system, those injectors can also be used in a method
of supplying a secondary fuel to an engine, and vice versa.
[0027] Generally, conversion or supplementation of a primary fuel
with a secondary fuel involves the addition of a secondary fuel
injector. However, determination of the amount of secondary fuel
necessary for delivery can be complicated. The actual determination
is dependent on a large number of variables related to the
environment and the functioning of the engine. Additionally, for
example, various engine parameters, including rpm, temperature,
load, etc., can affect the amount of fuel needed to run an engine
efficiently and effectively. Previous attempts to convert an
existing engine to run on a secondary fuel have largely been done
by selecting a fixed set of variables to determine an optimal
amount of secondary fuel. However, when the variables stray outside
the fixed set, both the performance of the engine and the quality
of the exhaust can be significantly degraded.
[0028] To overcome these problems, the present inventor has
recognized the need to develop a dynamic fuel delivery system for a
secondary fuel rather than rely on inefficient and inaccurate
static systems. As such, the present inventors have developed
dynamic secondary fuel delivery systems and methods that use real
time engine conditions and operating parameters to determine
substantially optimal amounts of secondary fuel to either replace
or supplement the primary fuel.
[0029] Modern car manufacturers use a computer called an engine
control unit that receives multiple inputs to determine an optimal
amount of fuel to provide a desired amount of power to the engine
while minimizing pollutants. Generally, the systems and methods
described herein can use the primary injector signal from the
engine's ECU to determine an accurate secondary injector signal for
a secondary fuel. Such methods and systems generally use a lookup
table that can be populated for various engine parameters to
provide an appropriate offset value for the secondary fuel rather
than a static preprogrammed value as commonly performed in the art.
The lookup table can be populated for a specific injector as well
as specific engine conditions that can affect an injector offset
value, such as, for example, fuel pressure differential between the
high pressure side and the low pressure side of the injector, as
well as injector voltage. As such, the present methods and systems
can provide a real time dynamic delivery of a secondary fuel
amount. The ability to dynamically alter the amount of secondary
fuel based on real time operating conditions of the engine enables
accurate delivery of an amount of secondary fuel that can provide a
desired power level from the automobile engine while minimizing
pollutants from the exhaust system. By using the primary injector
signal from the ECU and the dynamic operating conditions of the
automobile engine, an engine can be efficiently converted to use a
secondary fuel while maintaining or exceeding the automobile's
performance and pollution standards, as set by the auto
manufacturer that designed the car. This enables an automobile
engine to be converted relatively inexpensively to use a secondary
fuel while continuing to meet the fairly rigid standards set by
State and Federal environmental regulations.
[0030] The amount of primary fuel that is delivered to an engine is
determined by the ECU signal to the engine's primary injector. The
signal is typically a pulse width signal that instructs the
injector to open an amount of time that is proportional to the
length of the injector signal (pulse width) from the ECU.
Constantly changing engine parameters cause differing delays
between when the injector is instructed to open and when it
actually opens. This delay is referred to as a delay time, or
equivalently, as an offset value. For example, a change in voltage
at the injector can cause the speed of the injector to either
increase or decrease. Similarly, a change in fuel pressure
differential between the high pressure side and the low pressure
side of the injector can also cause the injector speed to increase
or decrease. The actual amount of time that the injector is open,
allowing fuel to flow, depends on these changing variables. For
example, an injector signal at a selected time may be high, or "on"
for 10.2 milliseconds (ms). However, the fuel pressure differential
and the injector voltage at the selected time may be such that the
injector is only open for 8.5 ms. Thus, there is a delay time of
1.7 ms.
[0031] In order to determine the actual amount of primary fuel that
is injected into the engine, a multi-dimensional table can be
created that shows the delay time of the injector for various
voltages and fuel pressure differentials. The delay time is
typically similar for a specific model of injector. A different
table can be created for each different model of injector that is
used. An injector can be characterized based on information
provided by the manufacturer. Alternatively, the injector can be
characterized by measuring the parameters for each table entry
using a laboratory setup.
[0032] The granularity of the table can be based on the accuracy
needs of the conversion. In addition, known algorithms can be used
to interpolate between values in the table, thereby enabling
increased accuracy without the need for extremely large tables. A
portion of one exemplary lookup table is shown in FIG. 1. In this
example a gasoline injector is shown. Similar lookup tables can be
constructed for diesel fuel injectors. Typically each lookup table
is unique to a particular brand, or type of injector. The table
shows delay times for a specific injector based on selected
injector voltages and varying changes in fuel pressure between the
high pressure side of the injector and the low pressure side of the
injector. While fuel pressure differential and injector voltage are
specifically identified as variables affecting the delay time,
additional engine parameters can also be taken into account and
used to refine the delay time in a multi-dimensional table.
[0033] As such, with this discussion and these definitions in mind,
the present application provides for a method 200 of determining a
secondary fuel amount for an engine, as shown in the flow chart of
FIG. 2. The method includes the operation of measuring 210 an
injector signal from the engine's Engine Control Unit (ECU) for a
first injector for a primary fuel to determine a timing value for
the first injector, wherein the timing value is related to an
amount of primary fuel to be delivered to the engine. Additionally,
the method can include the operation of determining 212 a delay
time of the primary injector using a lookup table configured to
provide the delay time of the primary injector. The delay time can
be used to determine an open time of the primary injector based on
a difference between the timing value and the delay time. The open
time can be used to calculate a predetermined amount of the primary
fuel to be injected into the engine during the primary injector's
open time based on the injection signal. Further, the method can
include determining 214 an amount of secondary fuel equivalent to
the amount of primary fuel. Also, the method can include
calculating 216 a secondary timing value for a second injector to
deliver the amount of secondary fuel to the engine in place of the
primary fuel.
[0034] Additionally, the method can further comprise measuring a
pressure differential of the primary fuel. The method can further
comprise measuring a voltage of the first injector. These
measurements can be performed at separate times or can be performed
at approximately the same time. In one embodiment, the pressure or
voltage may be substantially constant. In that case, the constant
value can be included in a lookup table, without the need to
measure the value. Additionally, the method can comprise
calculating a delay time associated with the first injector based
on the pressure differential of the primary fuel and the voltage of
the first injector using a lookup table.
[0035] Additionally, the method can comprise measuring a pressure
differential of a secondary fuel. The method can further comprise
measuring a voltage of a secondary injector. These measurements can
be performed at separate times or can be performed at approximately
the same time. Additionally, the method can comprise calculating a
delay time associated with the secondary injector from the pressure
differential of the secondary fuel and the voltage of the secondary
injector using a lookup table. Further the step of calculating the
amount of secondary fuel needed to provide the energy value can
include accounting for the delay time associated with the second
injector. In one embodiment, the method can further include
combusting the secondary fuel.
[0036] In another embodiment, a secondary fuel control system for
an engine can comprise a detector configured to detect a timing
value from an ECU injection signal for a primary injector. The
secondary fuel control system can include a lookup table coupled to
the detector and configured to provide a delay time of the primary
injector for injecting a predetermined amount of the primary fuel
into the engine. Additionally, the secondary fuel control system
can include a secondary fuel equivalent module coupled to the
lookup table and configured to calculate an amount of a secondary
fuel having an energy equivalent to the predetermined amount of
primary fuel by calculating an energy value of the predetermined
amount of primary fuel, calculating the amount of the secondary
fuel needed to provide the energy equivalent, and calculating a
secondary timing value for a second injector to inject the energy
equivalent of the secondary fuel into the engine in place of the
primary fuel.
[0037] In still another embodiment, a secondary fuel control system
for an engine can comprise an injection signal timing detector
configured to detect a timing value from an ECU injection signal
for a primary injector. The secondary fuel control system can
include a first lookup table coupled to the timing detector. The
first lookup table can be configured to provide a delay time of the
primary injector based on selected operational variables of the
engine. For example, the operation variables can include the
voltage at the injector and the fuel pressure differential at the
injector. The amount of the primary fuel that is typically injected
into the engine in response to the timing value of the ECU
injection signal for the primary injector can be determined in the
lookup table based on the value of the variables such as the
injector voltage and the fuel pressure differential. A second
lookup table can be coupled to a secondary fuel equivalent module
and configured to provide a ratio of secondary fuel to primary fuel
for the engine. The secondary fuel control system can include a
secondary fuel equivalent module coupled to the first lookup table
and the second lookup table such that the secondary fuel equivalent
module is configured to calculate an amount of a secondary fuel
having an energy equivalent based on the ratio of secondary fuel to
primary fuel by calculating an energy value of the predetermined
amount of primary fuel, calculating the amount of the secondary
fuel needed to supplement the primary fuel to provide the ratio,
and calculating a secondary timing value for a second injector to
inject the energy equivalent of the secondary fuel into the
engine.
[0038] Turning now to FIG. 3, an engine 310 can comprise an engine
control unit (ECU) 312 in communication with a primary injector
314. Additionally, the engine can be coupled to a secondary fuel
equivalent module 316. The secondary fuel equivalent module is
discussed in further detail in FIG. 4. The engine can be
connectable to a primary fuel 318 and a secondary fuel 320. As
described herein, the secondary fuel equivalent module can
calculate a timing value for a second injector 322. Generally, the
secondary fuel equivalent module can measure the timing value
associated with the primary injector and calculate the timing value
for a secondary injector in order to inject an amount of secondary
fuel sufficient to replace or supplement the amount of primary fuel
needed to sustain the desired operating condition of an engine.
[0039] Turning now to FIG. 4, the secondary fuel equivalent module
316 can be coupled to a detector 324 and can be further coupled to
a first lookup table 326 and a second lookup table 356. As such, in
one embodiment, the secondary fuel equivalent module can include
the detector and the lookup tables. However, such a configuration
is not necessary as the detector and lookup tables can be external
to the secondary fuel equivalent module. One or more lookup tables
may be integrated in or coupled to the secondary fuel equivalent
module.
[0040] Generally, the detector 324 is electrically coupled to the
ECU such that the detector can measure the injector signal of the
primary injector from the ECU. As such, the detector can be
configured to detect a timing value from the ECU injection signal
for a primary injector, generally determined by the timing of the
pulse width of the ECU injection signal. The lookup table(s) can be
a data array that provides the delay time for an injector based
upon various engine variables. For example, in one embodiment, the
lookup table can be used to provide a delay time associated for an
injector based upon the voltage of the injector and the pressure
differential of the fuel being injected by the injector. As such,
the present discussion is applicable to a primary injector used in
conjunction with a primary fuel. The discussion can also be
applicable to a secondary injector used in conjunction with a
secondary fuel.
[0041] The methods and systems described herein can have any number
of lookup tables. For example, in one embodiment, the methods and
systems can have a first lookup table that can provide a delay time
for a primary injector and a second lookup table that can provide a
delay time for a secondary injector. The delay time can be
calculated as described herein. In one embodiment, the delay time
can be determined from fuel pressure differential and a voltage
measured at the injector. Generally, such lookup tables are
predetermined and populated based upon manufacturing specifications
of the injector. Alternatively, the values can be predetermined and
populated based upon an array of measurements covering operating
conditions of the injector. Such an array can be experimentally
determined, as previously discussed.
[0042] Even though the present discussion refers to lookup tables
for providing offset values, the present invention can also include
lookup tables for providing a ratio of primary fuel to secondary
fuel based upon desired performance and/or engine characteristics.
Generally, the ratio can be predetermined and populated in a lookup
table and accessed by various variables, e.g., temperature, rpm,
load, etc.
[0043] Additionally, the secondary fuel equivalent module 316 can
further comprise an input 328 configured to receive a signal
containing information of a fuel pressure for the primary fuel to
calculate the delay time. The pressure of the primary fuel is
typically the difference (delta) between the high pressure side of
the injector and the low pressure side of the injector. The
secondary fuel equivalent module can further comprise an input 330
configured to receive a signal containing information of a low side
fuel pressure for the secondary fuel and an input 332 configured to
receive a signal containing information of a high side pressure of
the secondary fuel. As such, in one embodiment, the secondary fuel
equivalent module can calculate a flow rate of the secondary fuel
using the low side fuel pressure and the high side fuel pressure
information. This information can be used to determine how long the
secondary injector needs to remain open to allow the desired amount
of secondary fuel into the engine.
[0044] The secondary fuel equivalent module 316 can further
comprise an input 334 configured to receive a signal containing
information of a tank pressure for the secondary fuel to calculate
a fuel level signal for the secondary fuel. The fuel level signal
can then be used to provide a secondary fuel level via a fuel
gauge, fuel electronic display, or other appropriate device. The
secondary fuel equivalent module can further comprise an input 336
configured to receive a signal containing information of a
temperature for the secondary fuel. The temperature can be used to
calculate a density of the secondary fuel. The secondary fuel
equivalent module can further comprise an input 338 configured to
receive a signal containing information of the primary fuel level.
The primary fuel level can be modified to reflect the use of the
secondary fuel.
[0045] Additionally, the secondary fuel equivalent module 316 can
further comprise an output 340 configured to send a signal
containing information of a fuel pressure for the primary fuel for
use by the ECU. The secondary fuel equivalent module can further
comprise an output 342 configured to send a signal containing
information of a fuel level for the secondary fuel for use by a
fuel level indicator. The secondary fuel equivalent module can
further comprise an output 344 configured to send a signal
containing information of an injector pulse for the secondary
injector for the secondary fuel corresponding the secondary timing
value. Further, in one embodiment, the secondary fuel equivalent
module further can comprise a communication port 346 for
programming and diagnostic testing.
[0046] As described herein, in one embodiment, the delay times of
the first injector can be used to accurately calculate the actual
amount of primary fuel asked for by the ECU injector signal. The
delay time of the second injector can then be calculated in a
similar fashion to determine the length of an injector pulse needed
to allow a desired amount of secondary fuel into the engine using
the second injector. In one embodiment, the amount of secondary
fuel can have a substantially equal energy content as the amount of
primary fuel. Alternatively, the amount of secondary fuel selected
can be used to supplement the primary fuel, rather than replace
it.
[0047] The secondary fuel equivalent module 316 can further
comprise an expansion socket 346 for additional injector outputs.
Additionally, the secondary fuel equivalent module can further
comprise various detectors and electrical components (not shown)
for determining the various signals described herein. For example,
the secondary fuel equivalent module can further comprise a fuel
pressure detector for measuring the low and high side fuel pressure
of a secondary fuel and an electrical component for attachment of
the detector to the inputs described herein for communicating the
low and high side fuel pressure in the form of an electrical
signal.
[0048] In one embodiment, the amount of secondary fuel can replace
the primary fuel. In another embodiment, the amount of secondary
fuel can supplement the primary fuel. In one aspect, the secondary
fuel can account for at least 50% of the total fuel delivered to
the engine. In another aspect, the secondary fuel can account for
at least 90% of the total fuel delivered to the engine. Of course,
varying amounts of secondary fuel can also be used, including
without limitation, 60%, 70%, and 80%.
EXAMPLES
[0049] The following descriptions provide various example
embodiments. The representative examples are not intended to be
exclusive. The term "fuel pressure", as used in the examples, is
intended to mean a pressure differential between a high side and
low side of the injector. The voltage is measured at the
injector.
Example 1
Conversion of Gas to CNG
[0050] A gasoline (primary) injector pulse from an engine control
unit (ECU) is captured and is measured as 4.78 ms. The gasoline
injector offset value (delay time) is determined to be 1.22 ms. The
gasoline injector offset value is provided by a lookup table based
on current system voltage of the gasoline injector, 12.7 volts, and
fuel pressure of the gasoline, 43.5 psi. This offset value, 1.22
ms, is subtracted from the gasoline injector pulse, 4.78 ms, (4.78
ms-1.22 ms) to provide a gasoline injector open time of 3.56 ms,
which corresponds to the amount of gasoline delivered to the
engine. The actual amount of gasoline can be determined by
multiplying the injector open time by the flow rate of gasoline at
the current fuel pressure of the gasoline; i.e., 30 pounds/hour at
43.5 psi.=(30 pounds/3600 sec)=0.0083333
pound/sec.fwdarw.(0.0083333 pounds/sec*0.00356 sec), providing
0.0000296 pounds of gasoline per pulse. The gasoline pound per
pulse amount is then multiplied by a gasoline fuel stoichiometric
ratio; i.e., 14.7 pounds of air per pound of fuel, (0.0000296*14.7)
providing 0.00043512 pounds of air to combust each pulse
amount.
[0051] The amount of air needed to combust the gasoline can then be
divided by an alternate fuels stoichiometric ratio to find an
equivalent amount of secondary fuel to the gasoline. For example,
natural gas uses 17.2 pounds of air to combust one pound of fuel.
The amount of natural gas can be determined by dividing the air
required to combust the gasoline by the stoichiometric ratio
(0.00043512 pounds/17.2), which results in 0.000025297 pounds of
alternate fuel (natural gas in this example) per pulse for a
secondary injector. A flow rate of the natural gas for the natural
gas fuel injector (secondary fuel) can be determined at the current
fuel pressure of the natural gas and the temperature of the natural
gas using a lookup table. For example, at a temperature of 50 deg
and a fuel pressure of 150 psi=28 pound/hr=28 pounds/3600
sec=0.0077777 pounds/sec. The fuel demand, i.e., the amount of time
needed to deliver the natural gas, is determined by dividing the
natural gas needed by flow rate per second of natural gas injector;
i.e., (0.000025297 pounds/0.0077777)=0.00325 sec or 3.25 ms fuel
demand. The new injector pulse width for the secondary injector is
determined by adding the fuel demand to natural gas injector offset
at the current system voltage for the secondary injector and
natural gas pressure from a lookup table. For example, if the
voltage at the secondary injector is 12.5 volts and the fuel
pressure is 150 psi, a delay time of 2.94 ms can be determined from
a lookup table for the secondary injector. The total pulse width
for the secondary injector signal is the delay time of 2.94 ms plus
the injector open time of 3.25 ms for a total of 6.19 ms pulse
width for the secondary injector signal.
Example 2
Supplement of Diesel with CNG
[0052] A diesel (primary) injector pulse from an engine control
unit (ECU) is captured and is measured as 4.78 ms. The diesel
injector offset value (delay time) is determined to be 1.22 ms from
a lookup table. The diesel injector offset value is provided by a
lookup table, similar to the one shown in FIG. 1, based on current
system voltage of the diesel injector, 12.7 volts, and fuel
pressure (delta) of the diesel, 43.5 psi. The corresponding offset
value, 1.22 ms, is subtracted from the diesel injector pulse, 4.78
ms, (4.78 ms-1.22 ms) to provide 3.56 ms which corresponds to the
amount of diesel delivered to the engine during the injector open
time. This injector open time can be converted to an energy value
by multiplying the injector open time by the flow rate of diesel
fuel injector. The flow rate may be determined from a lookup table
at the current fuel pressure of the diesel; i.e., 30 pound/hour at
42.5 psi=(30 pounds/3600 sec)=0.0083333 pounds/sec. This value can
be multiplied by the injector open time (0.0083333 pounds*0.00356
sec), providing 0.0000296 pounds of diesel fuel per pulse. The
diesel pound per pulse is then multiplied by a diesel fuel
stoichiometric ratio; i.e., 14.5 pounds of air per pound of fuel,
(0.0000296*14.5), providing 0.0004292 pounds of air to combust the
diesel fuel.
[0053] The diesel fuel can be supplemented with a selected amount
of a secondary fuel, such as natural gas. A ratio of diesel to
natural gas can be determined from a lookup table based on desired
target variables, including, for example, engine temperature,
engine rpm, load etc. For example, a ratio of 20% diesel and 80%
natural gas provides (0.0004292 pounds*0.20)=0.00008584 pounds of
air for diesel and (0.0004292 pounds*0.80)=0.00034336 pounds of air
for natural gas. This amount of air to combust the diesel fuel is
then divided by the diesel fuel stoichiometric ratio; i.e.,
diesel=14.5 pound air for every pound of fuel, (0.00008584
pounds/14.5)=0.00000592 pounds of diesel fuel per pulse for the
diesel injector. A flow rate of the diesel fuel for the diesel fuel
injector (primary fuel) is determined at the current fuel pressure
of the diesel fuel. This can be determined using a lookup table.
For example, at a pressure of 15000 psi at 30 pounds/hr=30
pounds/3600 sec)=0.0083333 pounds/sec. The fuel demand, i.e., the
amount of time needed to deliver the diesel fuel, is determined by
dividing the diesel fuel gas needed by flow rate per second of
diesel fuel injector; i.e., (0.00000592 pound/0.0083333)=0.00071
sec or 0.71 ms of fuel demand for diesel. The new injector pulse
for the diesel fuel injector is determined by adding the fuel
demand to the diesel fuel injector offset at the current system
voltage for the diesel fuel injector and diesel fuel pressure.
These values may be determined using a lookup table. For example,
at a voltage of 12.5 volts and a pressure of 15000 psi, a delay
time of 2.94 ms can be determined from the lookup table. The total
injector pulse width is then the injector open time of 0.71 ms plus
the delay time of 2.94 ms for a total injector pulse width of 3.65
ms to provide the desired 80% diesel fuel to the engine.
[0054] The amount of air to combust for natural gas is then divided
by the natural gas fuel stoichiometric ratio; i.e., natural
gas=17.2 pounds of air for every pound of fuel, (0.00034336
pounds/17.2) providing 0.000019962 pounds of alternate fuel per
pulse for a secondary injector. A flow rate of the natural gas for
the natural gas fuel injector (secondary fuel) is determined at the
current fuel pressure of the natural gas and the temperature of the
natural gas. As previously discussed, the flow rate may be
determined using a lookup table. For example, at a temperature of
50 deg and a fuel pressure of 150 psi, the flow rate may be
determined to be about 28 pounds/hr=28 pounds/3600 sec)=0.0077777
pounds/sec.
[0055] The fuel demand, i.e., the amount of time needed to deliver
the natural gas, is determined by dividing the natural gas needed
by flow rate per second of natural gas injector; i.e., (0.000019962
pounds/0.0077777 pounds/sec)=0.00257 sec or 2.57 ms fuel demand.
The new injector pulse width for the secondary (natural gas)
injector is determined by adding the fuel demand to natural gas
injector offset at the current system voltage for the secondary
injector and natural gas pressure. For example, a lookup table may
be used to determine that at a voltage of 12.5 volts and a fuel
pressure of 150 psi the delay time is approximately 2.94 ms. The
total pulse width to deliver the desired secondary fuel per pulse
is the 2.57 ms open time (fuel demand) plus the delay time of 2.94
ms for a total secondary injector pulse width of 5.51 ms.
[0056] While the foregoing examples are illustrative of the
principles of the present invention in one or more particular
applications, it will be apparent to those of ordinary skill in the
art that numerous modifications in form, usage and details of
implementation can be made without the exercise of inventive
faculty, and without departing from the principles and concepts of
the invention. Accordingly, it is not intended that the invention
be limited, except as by the claims set forth below.
* * * * *